An internal investigation at a metro-area police department details "serious issues" - a cop who may have lied, a department that's been embarrassed.

"You can call it malfeasance or you can call it non-feasance," says Joel Friedman, a professor of law at Tulane University. "It was a consistent pattern."

The police don't want you to see their internal report; the department told us we couldn't have it. But a source handed it over: 53 pages of allegations of police misconduct.

"The best way to gain public confidence is to be transparent," Friedman insists. Without transparency, he tells us, "nobody's held to account. No accountability."

Those 53 pages of allegations lead to no demotions, no sanctions, little fallout.

"I believe this is a systemic, cultural problem," Friedman says. "If it wasn't a cultural, systemic problem it wouldn't go on and on and on. It wasn't one man, it wasn't one case, it wasn't one day. It was many officers over a long period of time with lots of cases."

Prior to being elected St. Tammany Parish sheriff, Randy Smith headed the Slidell Police Department. In 2015, he ordered an audit of his criminal investigations division.

A review of that audit brought us to the Madisonville home of a former Slidell cop, Mario Arthur. We wanted to ask him some questions about the report. Arthur wasn't there, though, and he never called us back.

According to the internal investigation, Arthur "had not been truthful", had "not worked the cases" or "dropped certain pieces of evidence" for 66 cases in less than two years - criminal cases that were extremely serious in nature.

"What is he doing? What is he get getting paid to do?" Friedman wonders. "And the answer is, he's probably not doing anything."

The cases include such serious crimes as child pornography, child molestation, the attempted murder of a 1-year-old, cruelty to a juvenile, arson, theft and simple rape.

Friedman says the report points to potential malfeasance in office. "Imagine you are the family of the victim," he suggests, "and you want justice and you want them to investigate and find out who did the crime against your relative... And this guy's not doing the job of investigating or, if he's investigating, he's not writing up the report."

Among the cases Arthur failed to properly investigate, according to the internal audit, was a 2014 case of alleged child pornography. That case featured images that were posted on Facebook.

The internal investigation found that a search warrant was sent to Facebook, but Arthur apparently made no follow-up with that company. No search warrant or return was ever dropped into evidence.

The audit says this was a case that could have "at least been solved with time and effort"; instead, it went nowhere.

In a case of child desertion, a 2-year-old was criminally neglected and left unattended outside his home, found sitting next to a pit bull. Nothing was done. The audit called the case "simplistic", but it's too late now to file charges.

When a housekeeper financially exploited a 91-year-old man, Arthur allegedly did nothing to follow up on his case. The audit says the case should have been worked in a timely manner and, with the suspect still out there, she could potentially be victimizing more elderly people.

The report also questions the head of the criminal investigations division at the time, Capt. John Gallaher.

The report says Gallaher had an inappropriate relationship with a female subordinate. Gallaher assured Chief Smith that the relationship would change. But the report says it did not.

The report also said Gallaher had to be counseled on his use of alcohol. And under his watch, the investigations division had an administrative collapse. But Smith never demoted or sanctioned Gallaher; instead, Gallaher was moved to another position in the department.

"The only action they decided, they thought was necessary, they move these guys over - don't discipline them, just move them somewhere else and bring somebody else in, and that will solve the problem," Friedman observes. "And I'm telling you, that is not likely to solve the problem."

The audit says the department has what's called a "Brady cop" - a cop who has been dishonest. The St. Tammany district attorney's office says Sgt. Kevin Simon lied in a narcotics report and Simon lied to the prosecutor. The DA's office "spoke about indicting Simon" for these matters - yet Randy Smith kept Simon in the narcotics division.

And just this year, new Slidell Police Chief Randy Fandal promoted Simon from sergeant to lieutenant.

Fandal denied our request for an on-camera interview. So did Randy Smith, the former chief who now leads the St. Tammany Parish Sheriff's Office.

This audit has been under wraps for almost two years. The department only issued a short press release when it was completed, noting Mario Arthur's resignation following an investigation - an investigation that, we now know, raised serious questions about some police officers who promised to protect and serve the citizens of Slidell.

The findings on Arthur were forwarded to the attorney general's office; there's no word on what happened to that investigation.